For reference, these are the changes being discussed: https://phabricator.wikimedia.org/F5022813
1) Significantly larger changes than this are happening all the time (the OOUI-ification of old forms, for example), without anyone noticing, so it's pretty clear people are reacting to the announcement here and not the actual change.
There is nothing wrong with not paying attention to something well outside your work area, and people should not be excluded from a discussion topic just because they are new (or casual) to it, but please consider how it creates an unhealthy community dynamic when people are criticized for announcing changes which would otherwise go unnoticed. There are already too many developers who avoid this list because they find it too stressful or time-consuming. One of the costs of transparency and open coordination is that discussions can get easily overwhelmed by a bunch of random people with strong principles but relatively little idea of what's going on (that's why wikis are so strict about canvassing, for example); it's a good mental habit to ask "would I have gotten involved in this discussion eventually even if it wasn't announced in a mailing list?", and if the answer is no, consider just moving on.
2) There was once a project to create a free encyclopedia, where every change had to be discussed and agreed on with half a dozen groups of stakeholders. It was called Nupedia; it produced a hundred articles in three years, while its offshoot Wikipedia did well over a hundred thousand.
It probably does not take a thousand times longer to discuss an article with various gatekeepers than it takes to write it. But it's sufficiently demotivating that people won't even try; instead they find a project where their contributions are welcome and not buried in red tape. Software development is not magically exempt from the same coordination costs that affect article writing. Please be mindful of unintentionally creating an unwelcoming environment.
It's not fundamentally different with staff members, either. They have more time, but that time is bought with donor money, which needs to be spent responsibly. Designers spending their time videoconferencing with every interested user on whether they plan to change the shade of the new message bar to a slightly different yellow some time in the next two years is probably not what most donors have in mind when they support the movement.
3) When you are asking people to do more early planning and announcement and discussion, you are asking them to do significantly more work. It's not a free lunch; they need to cancel some tasks they would otherwise have been able to do, and spend time writing emails and getting translations and setting up discussions instead. More discussion means less features. Sometimes that's a reasonable request; sometimes not. Please consider which one it is, before asking.
This time it falls squarely into "unreasonable", I think. Exactly what would an early announcement achieve? Delay producing the videos by half a year just to make sure the brightness of the ToC border is not 5% off? Or is "discussion" an euphemism for "veto power" and we should keep our website less accessible to readers with visual impairments so that the tutorial video colors are accurate?
Documentation decays; it's a sad fact of life. Developers are acutely aware of that, since they need to produce and maintain a lot of it. No one likes it, but there is no reasonable way to prevent it. Halting software development so that documentation can stay up to date is certainly not one.
4) On a more constructive note, there *is* a reasonable way to reduce template maintenance burden: make LESS available to template editors so that variables such as "ToC border color" can be shared between MediaWiki and userland code. I filed T152832 about that.